Species Rhyssomatus lineaticollis - Milkweed Stem Weevil

Common Milkweed Stem Weevil

Rhyssomatus lineaticollis (Say)

Orig. Comb: Rhynchaenus lineaticollis Say 1824

5.5-6.5 mm (1)

Det. R. Anderson, 2017

e NA to CO, UT (2)

prairies and pastures

mostly: May-Aug (BG data)

"A walk at Red Oak Prairie, [Allamakee Co., Iowa,] June 21, 2016 was the first time I had seen destruction of A. amplexicaulis plants due to insect activity. In fact, I would say the majority of clasping milkweed plants I found there that day were withered like the one shown; as I recall, it was easier to find withered plants than intact ones." - John van der Linden

"I split open this stem of clasping milkweed, Asclepias amplexicaulis, all the way down to the ground in search of the creature that had hollowed it out and caused the plant to wither; and there it was, finally, a small pale larva, as far down the stem as it could be without being underground." - John van der Linden

Adults initially feed on the apical leaves and then, after feeding, female weevils walk to lower parts of the stem and chew several sequential holes in the stem, creating a continuous scar. Females lay a single egg per hole and larvae complete development inside the stem while feeding on pith tissue. Oviposition scar length is an accurate predictor of the number of eggs laid by the adult female. (Agrawal, 2005)

in addition to feeding on the leaves and stems(5), adults also feed on milkweed buds and pods(6):

Lvs:

Buds:

Pods:

"Makes squeaking sounds when handled" - Lonny, pers. obser., 9 July, 2010

This weevil reduces the growth of Labidomera clivicollis and the more distantly related moth, Danaus plexippus. This effect is likely mediated by a reduction in plant quality.(7)

Rhyssomatus annectens (Casey)

- Range: e US

Blatchley and Leng (1916) report it as abundant on Asclepias incarnata (6)

but Bob Anderson thinks Rh. annectens might be a synonym of Rh. lineaticollis...

Agrawal, A.A. 2005. Natural selection on common milkweed (Asclepias syriaca) by a community of specialized insect herbivores. Evolutionary Ecology Research, 7: 651–667. (Full PDF)

Agrawal, A.A. & P.A. Van Zandt. 2003. Ecological play in the coevolutionary theater: Genetic and environmental determinants of attack by a specialist weevil on milkweed. Journal of Ecology 91: 1049-1059. (Summary)

Betz, R.F. 1989. Ecology of Mead's milkweed (Asclepias meadii) Torrey. Pp. 187-191 In Proceedings of the 11th North American Prairie Conference, University of Nebraska, Lincoln.

Betz, R.F., W.R. Rommel & J.J. Dichtl. 2000. Insect herbivores of 12 milkweed (Asclepias) species, Pp. 7-19. In: C. Warwick (ed.). Proceedings of the Fifteenth North American Prairie Conference, Natural Areas Association, Bend, OR. (3)

Dailey, P.J., R.C. Graves & J.M. Kingsolver. 1978. Survey of Coleoptera collected on the common milkweed, Asclepias syriaca, at one site in Ohio. The Coleopterists Bulletin, 32(3): 223–229. (8)

Fordyce, J.A. & S.B. Malcolm. 2000. Specialist weevil, Rhyssomatus lineaticollis, does not spatially avoid cardenolide defenses of common milkweed by ovipositing into pith tissue. Journal of Chemical Ecology, 26: 2857–2874.

Nishio, S., M.S. Blum, & S. Takahashi. 1983. Intraplant distribution of cardenolides in Asclepias humistrata (Asclepiadaceae), with additional notes on their fates in Tetraopes melanurus (Coleoptera: Cerambycidae) and Rhyssomatus lineaticollis (Coleoptera: Curculionidae). Memoirs of the College of Agriculture, Kyoto University 122:43-52.

Price, P.W. & M.F. Willson. 1979. Abundance of herbivores on six milkweed species in Illinois. American Midland Naturalist 101: 76–86. (9)

St. Pierre, M. & S.D. Hendrix. 2003. Movement patterns of Rhyssomatus lineaticollis Say (Coleoptera: Curculionidae) within and among Asclepias syriaca (Asclepiadaceae) patches in a fragmented landscape. Ecological Entomology 28(5): 579-586. (10)

Wilbur, H.M. 1976. Life history evolution in seven milkweeds of the genus Asclepias. The Journal of Ecology, 64(1): 223–240. (4)

Texas Entomology - Mike Quinn, 2009